1. Field of the Invention
This invention relates to ventilated footwear, and in particular, to a footwear ventilation system that uses a foot-actuated compressible air displacement chamber to draw fresh air into the shoe and to discharge hot and humid air out.
2. Background of the Invention
In addition to support and cushioning, a significant aspect of footwear comfort is the ability to dissipate heat and moisture. Excessive heat and perspiration in footwear can lead to comfort problems including malodor, blisters, and fungal growth. Unfortunately, manufacturers have favored designs improving lateral support, cushioning, and durability at the expense of heat dissipation. Specifically, materials added to enhance support and cushioning have increased the insulation surrounding the foot and the resultant trapped heat and moisture. In addition, cosmetic features on footwear have added layers of material that further exacerbate the heat dissipation problem. To alleviate this problem, users have turned to specialized socks that wick moisture away from the foot, deodorizing and disinfecting foot and shoe sprays, and deodorizing insoles. However, these incomplete solutions focus on the symptoms of the problem instead of removing the source.
Footwear ventilation systems known in the prior art have attempted to address the heat dissipation problem by removing excessive heat and moisture with a constant air exchange. However, in all cases, the ventilation systems reduce the cushioning capacity of other shoe components (e.g., the midsole), fail to move enough air to be effective, or are too complex to easily and inexpensively manufacture. The conventional system uses a collapsible chamber that is actuated by the cyclic downward force of the user's foot. The chamber is built into the midsole of the shoe and requires the removal of a significant portion of the midsole cushioning material. In addition, the typical ventilation systems incorporate at least two check or one-way valves: an inlet valve that only permits air to flow into the chamber, and an exhaust valve that only permits air to flow out. Typically, these valves are also contained in the midsole, further displacing cushioning material. Prior art designs have installed the air displacement chamber in a variety of midsole locations: in the heel, U.S. Pat. Nos. 1,660,698, 5,010,661, 5,606,806, and 5,697,171; in the forefoot U.S. Pat. No. 5,697,170; under the arch, U.S. Pat. No. 3,284,930; and extending the full length of the foot bed U.S. Pat. No. 4,602,441. In each case, the reduced midsole material detracts from the stability and support of the shoe.
U.S. Pat. Nos. 2,604,707 and 4,776,110 disclose designs in which the pumping chamber is located in a removable insole.
Some footwear ventilation systems in the prior art preserve marginal support and stability while providing adequate ventilation. However, in achieving this combination of cooling and cushioning, they suffer from increased complexity and cost of manufacture. U.S. Pat. No. 5,697,170 discloses a sole with multiple chambers filled with open cell foam. U.S. Pat. No. 5,655,314 discloses a network of channels through the cushioning material that collapse under the load. A bladder surrounding a central cushion is disclosed in U.S. Pat. No. 5,333,397. A central air chamber surrounded with cushioning is disclosed in U.S. Pat. Nos. 5,515,622 and 5,341,581. In most designs, the cushioning and re-inflation are the result of the properties of complicated peripheral cushioning material. U.S. Pat. Nos. 5,697,161 and 5,068,981 utilize springs within the air chamber. U.S. Pat. No. 5,655,314 incorporates cushioning into the air space in the form of domes or ribs. Thus, in each case, meeting the objectives of stability and cooling require a complicated and costly shoe design.
Thus, there remains a need for a low-cost, easily manufactured footwear ventilation system that provides efficient cooling and cushioning. The ventilation system must not compromise the flexibility and cushioning characteristics of the midsole, and optimally should use the ventilation system components (such as an air displacement chamber) to enhance cushioning. In improving cushioning, the ventilation system should provide a controlled deceleration of the shoe cushion, allowing a user to adjust the cushioning characteristics to her personal preference. Finally, the ventilation system should be modular and easily adapted to a variety of footwear designs.